Many medical procedures require samples of bodily fluid, such as blood, to be collected and analyzed. The samples often are collected in an evacuated tube that has a cylindrical side wall, a closed bottom and an open top. The open top is closed by a needle pierceable and resealable material. Evacuated tubes of this general type are sold by Becton Dickinson under the trademark VACUTAINER®.
Evacuated tubes typically are employed with a needle assembly and a needle holder. The needle holder typically includes a rigid cylindrical side wall with proximal and distal ends. The proximal end of the side wall is widely open and is dimensioned for slidable receipt of the evacuated tube. A distal end wall extends across the distal end of the tubular side wall, and includes an aperture for engaging the needle assembly.
The typical needle assembly includes a plastic hub configured to mount in the aperture through the distal end wall of the needle holder. The needle assembly further includes a proximal needle cannula extending proximally from the hub and a distal needle cannula extending distally from the hub. Safety shields are mounted releasably to the needle hub for covering both the proximal and distal needle cannulas prior to use.
The needle holder and needle assembly are employed by first removing the safety shield from the proximal needle and mounting the needle hub in the aperture of the distal end wall of the needle holder. Thus, the proximal needle projects into the needle holder. The distal safety shield then may be removed and the distal needle cannula may be urged into a blood vessel or other source of bodily fluid. Typically the health care worker will align the needle holder so that the bevel at the distal end of the distal needle cannula faces up. Thus the health care worker will have to rotate the cylindrical needle holder by hand to achieve the preferred bevel orientation. Additionally, the health care worker will want as small an angle of entry of needle cannula into the patient as is permitted by the geometry of the needle holder.
An evacuated tube can be inserted into the open proximal end of the needle holder after the blood vessel or other source of bodily fluid has been accessed. Movement of the evacuated tube into the needle holder urges the proximal needle cannula into the evacuated tube and places the low pressure interior of the evacuated tube in communication with the source of bodily fluid. Hence, a flow of the bodily fluid is generated into the evacuated tube. The evacuated tube is separated from the needle holder after a sufficient volume of the fluid has been collected. Additional evacuated tubes can be urged sequentially into the needle holder to collect additional samples.
The needle holder and needle assembly are withdrawn from the patient after a sufficient number of fluid samples have been collected. The distal needle cannula then is shielded to prevent accidental sticks, and the shielded assembly is discarded in a sharps receptacle.
Many different shielding mechanisms are commercially available. Accordingly, there is a potential for improper shielding of a used needle cannula due to a lack of familiarity with the particular shield. A demand exists for a shieldable medical implement with an easy and efficient shielding mechanism and with visual and tactile cues to ensure that shielding is carried out efficiently and correctly.